Vehicles may require a voltage source that provides a regulated voltage such as 12 VDC and/or 48 VDC. Internal combustion engine (ICE) vehicles use alternators that generate AC voltage, which is rectified to DC voltage. When the ICE is either operated intermittently (in a hybrid vehicle) or is absent (in a fuel cell or battery powered vehicle), an alternator can no longer be used to generate auxiliary DC power. DC power from a battery or fuel cell is the normal source of power for electric traction motors in such vehicles. DC/DC converters that are supplied by a high voltage DC bus are typically used to provide auxiliary power at a lower voltage level.
The reliability of DC/DC converters supplied by the high voltage bus needs to improve for automotive applications. DC/DC converters are also relatively expensive, especially when structurally enhanced to meet the tougher automotive applications.